Semi-automatic telephone system.



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SEMI-AUTOMATIC TELEPHONE SYSEM. APPLICATION FILED SEPT. la. 1901. neNEwED Nov. 21. 191s.

Patented Jan. 15, 1918i 5 SHEETS-SHEET 2.

77f60ifa G. MARTIN.

l SEMI-AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED SEPT. I3. 1907. REIIEwEn Nov. 27, I9Is. @l

KQMI

T. G. IVIARTIN.

SEMI-AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED SEPT. I3. |907. IIENIawED Nov. 27. |916.

Patented Jan. 15, 1918.

IIIIIIIIIIHI .1 .bm-SHEET 4.

T. G. MARTIN.

` SEMI-AUTOMATIC TELEPHONE SYSTEM.

`APPLICATION FILED sEPT.13. 1907. RENEwED Nov. 21. 191e.

L 2. Patented Jan. 15, 1918.

5 SHEETS-SHEET 5.

. To all whm it may concern." f

TALBOT G.MARTIN, 0F CHICAGO, ILLINOIS, ASSIGNOR, B'Y MESNE ASSIGNMENTS, T0

AUTOMATIC ELECTRIC COMPANY, A CORPORATION OF ILLINOIS.

SEMI-UTOMATIC TELEPHONE SYSTEM.

Application mea september 13,1907, serial No. 392,687,

Be it known .that I, .fIALBor G. MARTIN, aa citizen' of the United States oi America, andpresident of Chicago, Cook county, Illinois, have invented a certain new vand useful Improvement 1n Seml-Automatic Telephone Systems, of which the following is a specification.

My invention relates to yan.- automatic telephone system in which both manual and automatic apparatus is employed, such systems being ordinarily known as semi-automatic telephoneexchange systems.A Systems of this kind are some times developed from either automatic or manual systems p'robf system, inasmuch as the producer of automatic systems is now very often called upon to develop a'manual system into an vautomatic system. A system ofthis kind is some times called a cut-over system-that is to say, a system which is gradually .changed from enel-type to another, as from manual to automatic. The changing or cutting-over, ofcourse, is done gradually, and as muchas possible without interfering with' theservice between the different subscribers, so that during theperiod of alteration or change from one type t another some of the subscribers will be enjoyingyservice that is purely automatic. others will be receivnig seml-automatlc serv1ce, and

still othersJwill still .be subject to purely sary many, special provisions, both with respect to the automatic and the manual apparatus, because some of the manual apparatus must be modified for use in extendingconne'ction to orfrom automatic subscribers, while some of the automatic apparatus must be modified for use in extending connection to or from manual subscribers. ,Generally stated, therefore, the object of' my invention is the provision of an improved and highly-efficient semi-automatic telephoneexchange system.

Special objects of my invention are the provision oi an improved rotary connector adapted to automatically select trunks running to a branch or private exchange, and adapted to operate either as a common battery or'a-lecal battery connector, as hereinafter explained; the-provision of anim- Renewed-Novcmber 27, 1916. Serial No. 133,819.

v l proved trunkmg cord c1rcu1t and trunk line system for giving semi-automatic service phone-apparatus, th same being of such character that it is adapted for calling either manually or'semi-automatically, andv to ybc called either manually or semi-automatically; the provision of a subscribers line relay equipment of such' character that the line signal is blocked against operation when the subscriber calls automatically, and of such character that the subscribers can bel called manually or automatically, as hereinafter explained; and the provision of certain ldetails and features of improvement tending to increase the general eiiciency of a telephone system of this particular charxacter.

`To the foregoing and other useful ends,

my invention consists inl matters hereinafter f set Al'fnth and claimed.

In the accompanying drawings Figure l represents diagra'mmatically a private branch exchange to which there are allotted both manual and automatic substations A? and A, -respectively, and outgoing .trunk lines which terminate in a combined autolSpecification o! Letters Patent. l Patented Janfld, 1918.

matic'and manual main exfhange, in a system embodying the" princip es of my invention. f 4

Fig. 2 represents diagrammatically a manual common battery private branch ex-` change having trunk lines also leading to the main exchange.

Fig. 3 represents the manual section-of' the `main exchange, comprising multiple terminals of all they private branch exchange trunks, the subscribers of which section are equipped. with substations of the automatic type, but adapted to manual work.

vlig. 4 represents the automatic section of 100 the central office or main exchange switching apparatus having multiple terminals of all private branch exchange trunks.

Fig. 5 represents one `'of tlieautomatic substations, its selector D allotted to the automatic section (Fig. pled manual equipment. n The automatic substations may be of any 4), and its multisuitablevor approved type, but the substaztions, .like the;substation A, in connection .1.19

with which I have elected to illustrate my invention, -each comprises a receiver 2, a

switc-h-hook 3 for controlling th'ef'substation" series' with the condenser 33a across the line.

Furthermore, when the switch-hook is down the lsaid cam 5 disengages the springs 10 and 11, thus breaking the local circuit which in'- cludes in series the primary winding .12, transmitter 13 and local vbattery 14. The substation ground circuit is normally broken between the .ground springs 15 and 16 by the cam arm 6, but when-said springs are together, ground potential is provided to the ground post 17, and to the release spring 7,

as is usuallythe case in telephones of this type. The said substation comprises the usual induction-coil 18 having the primary winding 12 and secondary winding 19. Be`

ing an automatic substation it is provided with the usual vertical and rotary7 impulse springs 20 and 21. Said .-substatlon 1s, of

course, provided with a dial (not shown) which is secured to the shaft 22, together with the locking dog 23. Furthermore, there is a locking cam 24 that locks the dog 23 while the receiver is on the switch-hook to prevent a rotation of the dial. For operating the impulse springs 20 and 21 the substation is provided with an impulse wheel 25 that is secured to theshaft 22, which^impulse wheel carries-on its periphery the socalled vertical impulse teeth 26 and one rotary impulse ntoothv27. The said -impulse teeth are'so arranged that when the dial is drawn down the'impulse springs 20 and 21 are not carried `into contact with the ground post 17 ,but as the dial returns, first the vertical teeth engage the vertical impulse spring 20, and after they have completed their work the rotary impulse tooth 27 oper- -ates the rotary impulse spring 21. In this operationl the subscribers vertical line conductor 28 is first given a number of ground impulses, andthen the rotary line conductor 29 is given one ground impulse. It will be seen that as long as` the dial is out of normal position, the dog` 23. permits the secondary circuit-sprin 30 and 31 to separate, thus preventing t eimpulses that are -delivered to either line conductor from passing to the other. The signaling device comprises the push-button 34 which, when pressed, carries the spring 35 from the contact.pont 36 to the' grounded contact point 37. All of the- .automatic substatons-shoWnY in ,the various l diagrams are of the type -above described.

'.stated.- rlhe line conductorsof 'the 'saidv substation -I have multiple terminals inthe manual board, and also in a -first-'selector of the automatic exchange. The ringer 114 has the ringer coils connected" in multiple, and the local battery springjll is connected to ground, so that when the switch-hook is down the ringer s ring 116 is pressed onto the spring .115. there is an insulating bushing 118 which insulates the ringer connection tical line conductor.

Each subscriber of the automatic section is provided with a first-selector, such as the first-selector D (Fig. 5) or D (Fig. 4). These rst-selector switches D and lD may be of any suitable or approved type, forexample, ofthe general type f described in United States Patent No. 815,321, granted March 13, 1906, to Keith, Erickson and Erickson. Each selector embodies, amongother details, the following well-known devices and circuits (see Fig. 4). The switch shaft (not shown) carries the vertical and rotary wipers 38 and 39. respectively, and the private wiper.40. The side swltch is well known and comprises the side switch wipers 41, 42, 43 and 4 4, which may be designated as the vertical, rotary and private side switch wipers, and the rotary magnet wiper, respectively. The side switch is under the control of the privatermagnet 45, and when the side switch is in normal or iirst position the wipers 41, 42, 43 and 44 occupy the contact points 46, 47, 48 and 49, respectively. In the second position the wipers rest on the contact points 50, 51, 52 and 53, respectively, and in the third posilso, on the cam-arm 117 f from the ver- U tion -the contact points 54, 55, 56 and 57 are engaged 4by their respective wipers Through the medium of the vertical line relay 58, and whilethe side switch is in irst position, the subscribervcontrols thevertical magnet 59, which latter operates to raise the switch shaft and 'wipers 38, 39l and 40 vertically. By' means of the rotary line relay 60, and while the -side switch is in the first position, the. subscriber controls 'the private .magnet 45, and, therefore, the side switch. While the side switch isin second e whereby the subscriber controls the' release magnet 62 while the side switch is in the rst or second position.- If tho side switch 126, which have allotted to their use suitving operations through the medium of the side switch Wipers136` 137, 138`and 139. This connector is, in addition, provided with the private relay '140 which is controlled by i the rotary line relay 128, which latter in turn controls the private magnet 132, as Will be explained hereinafter. viding the connector with this automatic selective feature is as follows: A business office, or private branch exchange, for example, may be providedvvith three lines each terminating in a different telephone,`but all of Which are given the same number. then becomes necessary'to so arrange the connectors that if one line is in use the connector switch will 'automatically carry the calling subscribers line into connection with the second line, and if the second line is also in use the connection is carried to thethird line, and so on; and if all the lines are in use the connection is extended to a busysignaling circuit. The calling subscriber Would, of course, have no control over the apparatus as to With' which one of the set of lines he makes connection. This, of course, does not concern him, since, for the purpose of. his call, any trunk -line to the said oilice or private branch exchange Will do'. The arangement of the connector'banks is as fotlowsi If one office to which the number 2811 (see Fig. 1), for example, is allotted Wishes three telephones, he Will be given three lines terminating, one in the first contact of the vlirst level of the connector banks another in the second contact of the first level, and the 'third'in the third contact cf the first level.

. tact of the first level; but if the said contact is busy the connectoris automatically rotated onto the second set of contacts, or onto the third if the second is busy. It becomes desirable, as stated, to provide means for signaling the calling subscriber in the event that all three of the lines are busy. For this purpose the fourth set of bank contacts of the first level are connected with a busy-signaling circuit to the contacts of which the connector will rotate if all the lines are busy, A busy-signaling current is then sent out to the calling subscribers line over a circuit including the fourth set of contacts of this level. It will be evident that any ofce may be equipped with a number of lines, depending upon the number of contacts in the bank reserving the last contact for the busy con- The object` in pro? Itv ` the first contact of the set in the bank. As

shown in Fig. 3 the'substation K hasV been cut over or changed from a manual station to an automatic station, and, therefore, changed from the manual exchange to the automatic exchange, that it may be operated automatically to establish connections, instead ofhaving to call manually each time a connection is desired. To bring about this cut-over, the

-drop 119 is disconnected from the line conductors bythe insertion of insulation bef ltvveen thesprings 120, 121 and 122,' 123,

the condensers 280aL and 281*L are inserted in the manual line circuit, battery Bs connected to the springs of the bridge-cut-off relay of the first selector, and the Wiring of the ringer connections at the substation K is changed from the Wiring of the ringer 114 at `substation I to that shown at K or at substation A. In short, l representsanautomatic substation operating manually, and

at K is shownan exactly similar substation after it has been cut over to operate automatically. My improved apparatus and system is not only 4adapted to' semi-automatic Work, but is also adapted for a change or cut-over from a common batter telephone system to a local battery automatic telephone system. Of course, and as already indi-l cated, just before the cut-over all the subscribers Whose stations are to become auto matic are given, instead 'of a regular manual telephone, a .specially arranged automatic telephone I. which -V may continue to Work manually aslong as it is desirable, and

.at a suitable time the telephone is ina few minutes changed to the form shown at K, from Which it continues to Work automatically the line-signal' relay springs havingl also been re-arranged, as already indicated.

The operation of the system may be more clearly understood by considering its operation when one subscriber calls another. Suppose that thesubscrber at substation A, which is a substation of the private branch exchange shown in Fig. 1, desires to establish connection with the automatic substation A shown in Fig. 5, on the line #2220 which is allotted to the main central'exchange. In that event, the calling subscriber` at substation A removes the receiver 2 from the switch-hook 3, whereby the secondary Winding 19 in series with the recelver 2 1s bridged across the line` conductors 28 and 29.

This closes an energizingwcircuit through the line relay 141, extending from ground Gr2 through the jack springs 142 and .143, vertical line conductor 28, secondary springs 30 and 31, signaling device, secondary winding 19receiver2. rotary line conductor 29,

passes to the third position then, since the selector D is of the trunk-release type, the

,selector D is controlled through the neXt switch with which a connection is then established, and through the private wiper 40, and by means of the back-release relay 63. The bridge-cut-of. relayl 64 is provided to open the connection between the line relays 58 and 60, and between said relays and battery B. This isdesirable, because if the relays are'not disconnected from each other 4and from the battery, the ringing current zoA etc.

for signaling the subscriber may operate.

either or both ofthe relays 58 and 60 and cause some interference with the switch. It

is also desirable A'to remove the bridge formed through the said relays from across the line normal conductors 65 and 660i the selector normal .conductor 67 ofthe selector D, is l of no utility in connection with lthe secondselector and is also omitted. Since like parts are likewise represented throughout the drawings, the vertical magnet 68 and the rotary magnet 69, the release magnet 70 and the private magnet 71 will be recognized and understood. .The said private magnet 71, of course, controls ythe side switch wipers 72, 73, 74.and 75, the said privatemagnet alsoA controlling the circuit ot,thel vertical magnet 68, in the usual manner, by means of the springs 76 and 77', butl not of` the release magnet, for the release magnet spring is omitted. The vertical movement of the switch shaft, and, therefore, of the -wipers 7.8, 79 and 80, is controlled by the 50' vertical magnet 68, and the rotary movement by the, r0tary magnet 69, the rotary magnet circuit being provided with the usual interrupter springs 81. The operative magnets of theswitch are, of course, controlled bythe subscriber through the `medium of vertical and rotary line relays 82 and 83,. as is well known. Said relays have under their control the usual springs 84,' 85 and 86, and in addition the trunkv release springs 87` and 88, whereby the said switch may be releasedwhen the side switch wipersfae in ii-rst or second position.

The connector switch F may also be of any suitable or approved type, for instance of the rgeneral typedescribed 1n United States to Keith, Erickson and Erickson. The connectors, of course, are used to complete the connection to some given telephone line leading to some subscribers station 0r other line, as will be explained vwith reference to the connector L. The mechanical details of the first-selector and connector, as is well known., are very much the same. For example, the connector switch shaft (not shown), like the vfirst-selector switch shaft,"' carries the line wipers 89 and 90 and the private wiper 91. The connector switch is also controlled by the calling subscriber through'the medium of the -vertical and rotary line relays 92 and 93. The vertical line' relay directly controls the vertical magnet 94, and also the rotary magnet 95 and ringer relay 96. The function of the vertical magnet 94 is to give the shaft and shaft wipers their vertical motion, and the rotary magnet 95 imparts to the shaft and shaft wipers a rotary or circular motion. The rotary line relay controls `the private magnet 97, which latter undercertain conditions controls in turn the verti- -cal and rotary magnets 94 and 95, release magnet 98 and also the side switch wipers 99, 100, 101 and 102. The side switch of the connector, like the side switch of the firstselector, has a normal or first position, a second position and a third position. The release magnet.98 is also controlled by the line relays 92 and 93 conjointly. By the condensers 103 and 104 the circuit through the'connector is divided into two sections. The back-bridge relays 105 and 106 giveto the called subscriber means whereby he may release the connector switch that has been connected with. his line. The central olice isequippedwith a busy-signaling apparatus of any suitable design, as, for example,'the one comprising an interruptefi` 107 in series with'the primary windin 108 of the induci Patent No. 815,176, granted March 13, 1906,

tion-coil 109, whereby a usy-signalingcurrent 'is induced in the secondary winding 110 of the said coil. The connector switch shaft alsocarries a normal post arm 111 which, when the connector shaft is 0E normal, allows the spring 112 to engage the ycontact point 113, whereby the busy-signaling current passesA to the line of the calling subscriber when the side vswitch is in first position. The connector switchh shown in Fig. 4 is of the rotary type-that is, means are provided whereby the connector shaft may be made to automatically rotate to pass over a busy Contact of a set of lines, and to stop-on the first oneof that-"group which is idle. -In other words, the connector L combines the general features ofthe connector with those of the first-selector. The lcon- A nector switch L is an improved form of the said general type. The usual switch shaft A of'saidconnector is-provided with' the line -wipers -124 and`125f andflthe private wiper.

through the jack springs 144 and 145, line relay 141 to the battery lead 146, thence through battery B and to-ground G. The said relay, upon energizing, attracts its armature 147, whereby a circuit is closed through 'the line lamp 148. This circuit extends from ground G2 through the lamp 148, contact point 149 and armature147 to the battery lead 146, thence through battery Band to ground. The operator, in response to the signal, and learning that an outside connection is desired, inserts the plug p into the jack j, and operates the key k so that the springs 150 ,and 151 and 152 and 153 engage, whereby thecondensers 154 and 155 are bridged or shunted bythe coils 156 and 157. Thesubstation A is now I connected with the trunk line conductors 158 and 159, which terminate in the first-selector yD (F ig.

4). r1`he calling operation by which the subscriber A, for example, would call and signal subscriber A is as follows: To call' the number 2220, which is arbitrarily chosen as the number of the substation A, the subscriber at substation A operates his calling devicefin a suitable manner, corresponding to each digit. For each digit the vertical line is grounded a certain number of times, corresponding to the numerical value of the digit, andthen the rotary side of the line is grounded once. The first digit Ibeing 2, the calling subscriber at substation A turns his dial for the first digit 2, thereby grounding the vertical. line conductor 28 twice and .the rotary linelconductorf 29 once upon the return motion ofthe dial. The ground potential to the line conductors 28 and 29 is then transmitted to the trunk line conductors 158 and 159. Grounding the vertical line 'conductor 28 energizes the vertical line relay 58 of the rst-selector D. The circuit i through said vertical line relay extends from ground G through ,the ground springs 15 and 16 to the groundpost 17, thence to the vertical impulse spring 20, vertical line conductor28, vjack spring 143, plug' p, springs 172 and 173, conductor 174, through the' key y sprin 153 and 152, relay'157, springs 17 5` and 1 6, vertical trunk conductor` 158 to the side vswitch wiper 41, -contact point 46, through the vertical line relay 58 to the bridge-cut-oi springs v166 and 165, to the lbattery lead 167 thence through' battery B time established through the vertical magnet and to ground.` Y Each` time that'the vertical line relay 58'is energized the vertical line relay *springs 168. and 169 are pressed into contact, and an energizing circuit is each The vertical magnet 59 being operated twice,

the first-selector switch shaft and wipers 38, 39 and 40 are raised two steps. The said Wipers are carried to a level with the contact points that constitute the terminal of the trunk line leading to the selector switch E. Following the vertical impulse the rotary impulse spring 21 is grounded once by the rotary impulse. tooth 27, thereby grounding the rotary line conductor 29 once and energizing the rotary line relay 60. The path of this energizing circuit is from ground G through the ground springs 15 and 16 to the ground post 17, rotary impulse spring 21 to the rotary line conductor 29, jack spring 144, springs 160 and 161, conductor 162,A

springs 150 and 151, relay 156, springs 163 and 164 to the rotary trunk line conductor 159, side switch wiper 42, contact/point 47 to-the rotary line relay 60, thence to the bridge-cut-ofl'I springs` 177, 166 and 165 to the battery lead 167 thence through battery B and to ground. The rotary line relay, upon energizing, presses the line relay springs 178 and 1684into contact, thereby establishing an energizing circuit through said magnet passes from groundG3 through the springs 168 and 178 to the private magnet 45 and battery lead 167, thence through battery B and to ground. The private magnet being energized for a moment and y the private magnet 45. -The current through banki lcontacts that constitute the terminal vof a trunk line leading to the selector switch E. If the rst trunk line is busy an energizing circuit is established through the private magnet 45, when the private Wiper 40 engages the grounded contact, thereby 1retaining the side switch in second position and maintaining the circuit through the rotary magnet 61. The rotary magnet, by intermittent magnetization, causes the shaft wipers to rotate past the last busy trunk line. However, as soon as the private magnet deenergizes, the side switch is tripped into third position; or if there. are no busy conytacts to be passed over, the rotary magnet 61, as -is Well known, trips the side switch to third position, when the wipers engage the first trunk line,"with the result that as soon as the side switch `wipers 41 and 42 vengage their respective contacts 54 and 55 the subscribers line is extended to the selector switch E. Also, since the side switch wiper 43 engages the grounded contactpoint 56, a guarding potential is established at the private'wiper 40' for protecting the seized. trunk line to the selector -E-from being molested by any other switch. This guarding potential also protects the calling trunk line by establishing a guarding potential at the connector bankover the private normal conductor 67. 4The second digit is called after the subscriber has established connection "with the selector E, by way of the trunk line .leading to the connector F. Thethird nector.

digitv operation of the dial, since the subscribersI line conductors are extended cto the connector F, is directed to the said con- Grounding the vertical trunk conductor 158 for the third digit energizes the vertical line relay 92 of vthe connector F. The current through said relay flows from the substation ground G', as previously traced, to the vertical trunk conductor 180, to the vertical line relay 92, thence to the battery lead 167, and through battery B to ground. The vertical line relay- 92 in A turn presses the line relay springs 182 and 183 intol contact, and as a result the magnet 94 is operated.4 The current thro-ugh the said magnet flows from ground G5 to the springs 182 and 183, private magnet springs' 184 vand 185, side switch wiper 102, Contact point 186, vertical magnet 94 to the battery lead 167, and through battery B to groun The vertical magnet 94, as usual, Aoperates to raise the switch shaft.. Being operated ltwice the shaft is raised two steps, and the shaft Wipers 89, 90 and 91 are carried to 'a point opposite the level yin which the line of the substation #2220 is located. -When the rotary trunk conductor 159 sis-grounded the rotary line relay 93 of the connector F is operated. The current flows through the rotary relay 93 from the substation ground to the rotary trunk conductor 159, as previously traced, rotary line relay 93 to the battery leadv 167, thence through battery B and to ground. `The rotary line rela 93 in turn energizesthe private magnet 9 aupon pressing the line relay springs 188 and 182 into contact. The current through the said private magnetv passes from ground f-r" through the springs 182- and 188, private magnet 97 to the battery lead 167,- thence I through battery B to ground. The private magnet being operated causes the'side swtcl to pass from first to second position. As a result the side switch wiper 102 shifts into engagement -with the contact pointy 189, therebysubstituting the rotary magnet 95 for the vertical magnet 94 to bring the magnet 95 underthe control of the vertical line relay 92. `The fourth digit operation of the dial causes thel vertical line conductor 28 to be grounded vten times, since the fourth digit is the digit 0. Each time that the vertical trunk conductor 158` is grounded j the vertical line relay 92 of the connector F is operated over circuits that have been pointed`out; but instead of operating the vertical magnet 94 it operates the rotary magnet 95 each time. The circuit through the said rotary magnet extends from ground G5 .to the side switch wiper 102, thence through the contact point v189 to the said rotary magnet 95, to the battery lead 167, and through battery B to ground. The switch shaft is thus rotated step by step until'the Wipers 89, 90 and 91 are carried into engagement with the normal conductors 190, 191 and 192 that extend to the firstselector D of the called line. The conductors 190 and 191 continue to the called subscribers line and to the substation #2220 (Fig. 5).- Grounding the rotary line conductor 29 for the last time energizes the rotary line relay 93 of the connector F, the 'energization of which relay causes either the release of theconnector switch if the called line is busy, or the release of the side switch from second to third position if the line is not busy. It will first be assumed that 4the energization of the-rotary line relay 93 produces the latter result*that is, releases the connector side switch to third position, which latter operation places the side switch wipers 99 and 100 in engagement with the contact points 193a and 194, thus placing the calling subscribers line in connection with the called subscribers line through the -condensers 103 and 104. This connection is marked by heavy lines in Figs. 1, 4 and To signal the called subscriber the calling subscriber presses his signaling button 34, thereby grounding the vertical line conductor 28 o-ver a circuit that extends from ground G through the ground springs 15 and.16, contact point 37, spring 35 to the 195l and 196, thus breaking the connection intacta between the callin subscriber and the called subscriber, and bridging the ringergenerator 197 across the called subscribersNline for ringing the bell 198 at the station ofthe latter. In order to prevent the ringmg current from interfering with the line relays 199 and 200 of the called first-selector D the bridge-cut-oif relay 201 is energized as soon as the connector side switch wiper 101 `engages the grounded contact point 202. The circuit through said bridge-cut-'oif relay extends from ground G11 through the side switch wiper 101 to the private wiper 91, to the bridgefcut-off relay -201, thence to the battery lead 167, and through battery B to ground. The said relay 201, 'upon energizing, separates its springs, thereby breaklng the connection between thefsaid relays 199 and 200 and battery lead, and between each other, leaving the line clear at the selector D. rlhe same circuitthat connects the side switch wiper 101 with the connector shaft private wiper 91 is used for establishing a guarding potential that protects the seized line from linterference by some other subscriber. The two substations A and A being thus connected, communication may be carried on over the connecting' circuit shown in heavy lines in Figs. 1, l and 5. l

The release of the central ofiice switching apparatus occurs when the calling subscriber restores the receiver 2 to the switch-hook 3, thereby pressing the release springs 7, 8 and 9 into engagement for a moment. rlhe contact of the said release springs grounds the vertical and rotary line conductors 28 and 29 simultaneously from ground G to the release spring 7 thence through springs 8 and 9 to the vertical and rotary line conductors, thereby simultaneously energizing the connector vertical and rotary line relays 92 and 93, whereby the release. relay 203 of the selector E is included4 in a series circuit with the release magnet 98 of the connector F. The path of the circuit extends from ground G8 at the selector-E to the side switch wiper 74, release relay 203, selector shaft wipervSO,

connector release: 'springs 204 and 205, re-

lease magnet 98 to the battery lead 167,.

thence through battery B. and to ground.

When the connector release magnet 98 isthus supplied with current it energizes, and as a result the switch shaft and side switch are restored to normal position, thus breaking the 'connection between the connector switch shaft wipers .89, 90and 91 and the normal conductors 190, 191 and 192. The

Aback-release relay 203 of the selector E, be-

ing in the same circuit with the release magnet 98, energizes simultaneouslyI with the latter and presses the springs 209 and 210 into engagement, which in turn close an energizingjcircuit through the release magnet 70 of the selector E in-series `with the release relay 63 of the selector D. This circuit extends from ground (l9 through the release relay 63, shaft wiper 40, springs 209 and 210, through the winding of the release magnet to the batteryl lead 167, thence through battery B and to ground.. All ofthe relays andl magnets thus energized attract their re- ;Spective armatures and remain in readiness to release their respective switches, and as soon as the substatlon release springs 7, 8 'and 9 separate and break the ground connection with the line conductors 28 and d29 they again den'ergize. The calling lsubscriber thus restores all switching apparatus which he originally brought into use. When the line conductors 28 and 29 are grounded simultaneously the relays 156 and 157 of the private branch exchange energize simultaneously, whereby the springs 211 and 212 engage, as a result closing a circuit through the drop 213. At no other time do the springs 211 and 212 engage, the adjustment being such that only when the said two relays energize simultaneously, as during the release, are thesprings 211 ancl-212 placed in contact. The circuit through the drop 213 extends from ground G10 through the drop 213, springs 211 and 212 to the battery lead 146, thence through battery B and to ground. rlhe operation ofthe drop indicates to the operator that the subscriber at substation A has vacated the trunk line. The plug p is then removed from the jack j and the key la is restored to normal position, thereby returning the trunk line to normal Condition.

lf the called line #2220 is busy at the time that the calling subscriber attempts to establish connection, the connector F is released by the last impulse to the rotary line lconductor 29 as follows: Said impulse energizes the rotary line relay 93 of theconnector F, which relay inl turn energizes the private magnet 97, pressing the private springs 202a and 203EL into contact after the private wiper 91 has been carried onto the private bank contact. Of course, it is understood that whenever the line #2220 is busy the connector private bank contacts` connected with the private normal conductor 192 are all connected to ground. Therefore, since the connector side switch is in second position when the private magnet springs 202L and 203L are brought into contact, an energizing circuit is established through the release magnet 98 from the said grounded private bank contact to the private wiper 91,` thence to the side switch wiper 101 (which is in seco-nd position) to the private magnet springs 202a and 203, through the winding of the release magnet 98 'to the battery lead 167, thence through battery B to ground. The connector switch shaft and side switch are thus released and connection is not es'- tablished with the called line. Now, when the calling subscriber presses the signaling button 34 the vertical line relay 92 becomes' energized' and operates to close a circuit through th'e' vertical magnet 94. The vertical magnet operates to carry the switch shaft vertically, whereby the' oit-normal springs 112- and 113 engage to permitthe busy-signaling current to pass to the calling subscribers line, in the usual way. The subscriber, upon hearing the busy-signal, restores his receiver to the switch-hook, whereby the release springs 7, 8 and 9 are pressed into contact and an energizing circuit established through the connector vertical and rotary line relays 92 and 93, as already explained, producing the release of the switching apparatus, as stated. The operator is given the disconnect signal by the operation -of the drop 213 in the manner explained above. v

ticular hundred-group to which vthe rotary 5 If the subscriber at substationA 5), for example, desires to speak to the subscriber A2 ofthe private branch exchange (Fig. 1), the first-selector D and some second-selector, 'E for example, are operated,.

in the manner just described, to establish 4connection with the trunk conductors 214,

215 and 216 which lead to the rotary connector L. These rotary connectors, of course, v

may be accessible only from some one second-Selector level-in this case the eighth level-since the rotary. connectors of thel main automatic exchange are allotted to one particular hundred-group, and all of the trunk lines leading to the various private branch exchanges may -terminate in this par- L. The vertical impulse energizes the vertical line relay 127, and the vertical magnet 129 is in turn energized, andl the shaft wipers 124, 125 and 126 are raised opposite the first level. The rotary impulse operates the rotary line relay 128, which upon energizlng closes a circuit through the pri- .vaterelay 140. This circuit extends from ground G19 through the springs 206 and 207, through the'private relay 140 to the battery lead 167 thence through battery B and to ground. The private relay 140 energizes and closes a circuit through the private magnet I magnet 132 to the battery lead 167,

132, said circuit extending from ground Gr12 through the springs 219 and 220 pr1vate thence through battery B -and to ground.- The private magnet, upon energizing and deenergizing, permits the Iside switch to pass to second position. The last vertical im" pulse operates` the rotary magnet 130 in the usual way, and the last rotary impulse energizes the private relay 140, which operates to close a circuit through the private magnet 132, which now operates to immediately release the side switch from second to third position, which closes connection with the irst line of the group; or, possibly, the private magnet is energized to .lock the side switch in second position to causev the connector shaft to automatically rotate onto the next idle contacts. Of course, if the second set of contacts leading to the ofiice desired are busy, thee connector shaft Wipers are rotated to the third trunk line, etc. Furthermore, if all of the trunk lines to which the number 2811 is allotted are engaged, th:

shaft wipers are rotated onto a set of contacts to which the busy-signaling machine M v is connected, and the calling subscriber receives the busy-signal. This automatic rota# tion is brought about as follows: When the private relay 140 energizes, the private magnet 132 is energized, as previously explained, and is maintained energized if the first rivate contact is grounded-that is, if the first trunk line is in use. The locking or holding circuit for'the private magnet extends from the grounded contact to the private wiper 126, side switch wiper 138, contact point 221, private magnet springs 223 and 222, private magnet 132 to the battery lead 167, thence through .battery B and to ground. The private magnet 1 32 is thus energized by a locking circuit and retains the side switch wipers in second position as long as the wiper 126.l engages 1a. busyf or grounded contact. Furthermore, when the private magnet is energized the spring 224 is shifted from the spring 225 to the spring 226,

whereby anew energizing circuit is completed through the rotary magnet 130. This circuit extends from ground G13 through the interrupter springs 2279, private relay springs'228a and 229", private magnet springs 226 and 224, side switch wiper 139, contact point 227, rotary magnet 130 to the battery lead 167, thence through battery B `and to ground. The connector now operates to rotate automatically as long as the shaft wiper 126 engages a grounded contact point.

When the shaft 'wiper 126v leaves the last busy contact the circuit through the private magnet is broken, whereby the said magnet denergizes and the side switch passes to. third position. If lthe first set of contacts is not in` use there is no ground potential at the private wiper 12,6 to lock and hold the private magnet when the last rotary impulse comes, and therefore the side switch passes to third position. At any rate, when the side switch passes to third position, andI when the side switch wiper 138 engages the contact point 228, a guarding potential is established at the connector -private bank for protecting the seized line. Assuming that the connector L has engaged the terminal contacts of the normal conductors 65, 66

and 67 of the trunk line .conductors 158 and 159, then this guarding potential closes an energizing circuit through the bridge-cutoff relay 64 of the first-selector D. Also, at the instant that the side switch Wiper 138 engages vthe grounded contact point 228 an energizing -circuit is established through the switching relay 229 to the battery lead 167, thence through battery B and to ground. The said'relay, uponenergizing, operates -to shift the springs 230 and 231 to the springs 232 and 233, respectively. The engagement of the springs 230 and 232 connects the back-bridge impedance coil 134 with the battery lead 301, and the engagement of the springs 231 and 233 connects the back-bridge impedance coil 135 With ground. After the shaft wipers 124 and 125 have connected with the normal conductors 65 and 66, respectively, then at the instant that the side switch wipers 136 and 137 engage the con- Vtact points 234 and 235 an energizing circuit is established through the ysignal relay 236 (Fig. 1) at the private branch exchange. rlfhis circuit extends from ground Gr15 through the springs 233 and 231, coil 135, vrotary conductor, through the ringer relay springs to the side switch wiper 137, shaft wiper 125,

rotary normal conductor 66, rotary trunkC conductor 159, springs 164 and 163, conductor'237, springs 239 and 238,` relay 236 to the vertical conductor, springs 175 and 176 to the vertical trunk conductor 158, vertical. normal conductor 65, shaft wiper 124, Contact point 234, side switch wiper 136, through the ringer relay springs to the vertical conductor, impedance coil 134, s rings 230 and 232 to lthe battery lead 301 (Fig. 3),

`desired line. the plug engages the ring of. the jack j? an thence through AVbattery Bs and to ground.

'The relay 236, upon energizing, attracts its armature 240 against the contact point 241,

whereby an energizing circuit -is closed through the drop 213. This circuit extends from ground G10 through the said drop, contact point 241, armature 240 to the battery lead 146, thence through battery B and to ground. The operator, in response to the drop signal, operates the key 7c. to bridge her talking set across the extended trunk conductors 158 and 159, andupon learning that substation A2 is desired inserts the`plug p into the jack jf. Of course, had4 the subscriber at lsubstation A desired connection .with any other subscriber of the private branch exchange, such a's the subscriber at substation A, the perator would insert the plug p into the jack corresponding to the However, when thev ring of Vbattery lead 146, thence energizing circuit is closed through the re.

leasing relays 242 and 243, as follows: From l ground G1 through the jack .7'2 and plug 'p to the conductor 244, springs 245 and 246,.

conductor 247, relays- 242 and 243 to the bat tery lead 146, thence through battery B and to ground. The said release relays attract their respective armatures, and when the armature 248v engages the contact point 249 a circuit is closed through the supervisory lampl 250 extending from. ground G22` through ,the springs 251 and 252, contact point 249, armature 248, conductor 253, contact point 254, armature 255, lamp 250 to the battery lead 146, thence through battery B and to ground. The further use of the release relays will be explained hereinafter. After the plug p is inserted into the 'jack jz, the key 7c is operated to disconnect the extended trunk line conductors 158 and 159 from the line conductors of the called substation, and to bridgev the ringer generator 256 instead. The subscriber at substation` l thereby indicating to the operator that the subscriber at substation Az'has answered.

'llhe release of the central oiice'vswitching apparatus occurs, as previously explained, when the calling subscriber grounds both line conductors simultaneously upon the restoration of the receiver to the switch-hook. When thesubscriber at substation A2 restores his. receiver v'to the switch-hook the energizing circuit through the relay261 is broken, and the armature 255 returns to normal position in Contact with'the point 254, thereby. completing the circuit through the supervisory lamp 250, indicating to the operator that the established connection has been abandoned.' The operator then re.

moves the plug p from the jack jz and also restores the drop 213. When the ring of. the plug disengages from the ring of the Jack the ground G1 relays 242 and 243, thus vpermitting the said relays to Adenergize, andthe armatures to return to .normal position, thereby breaking the circuit through the supervisory 4lainp250 when the armature 248 leaves' the contact point 249.

lWhen the subscriber atsubstation A calls a subscriber, A for example, of the manual is cut oil" from the release whereby the circuit through the supervisory lamp 2501s broken,

private branch exchange (Fig, 2), the central oiice switching apparatus, including the.

first-selector D', assecond selector'E and a rotary connector L, is operated inthe manner already'explained, to establish connection with a trunk line leading to the branch exchange. The operator in turn, in the usual manner, completes the connection by inserting the plug p into the jack of the deslred line.

The substation A may be operated, in the usual manner, to establish connection with vthe substations K and I. I n each case there is a busy-test upon the corresponding jack at the `manual board of called line. This busy test is provided by the corresponding switching relay on the manual"board, the said relay being energized through the'private wiper of the connector and the private normal. A busy test is also provided from the private wiper to all multiple connector private bank l contacts, as usual. This is, of course, to protort the called line. The calling line is iprotected in a similar manner by the rstselector as soon as the switch shaft rises. This is true with regard to all li-nes operating automatically. l

, Suppose that the subscriber at substation A2 desires connection-with the substation A3 (Fig. 2) of the manual private branch exchange. In thatevent, the 'operator at the branch exchange shown in Fig. 1 is signaled and given the number of the exchange in Fig. 2. The operator answers the calluwith a local plug, but upon receiving a number of the exchange in Fig. 3 she removes the local plug and inserts the plug p into thejack jz.'

'Assuming this number to be 2821 the key lc' is operated to move the springs 176 and'164 264 in the Second level leading to the manual from the springs 175 and 163 to the springs 262 and 263, whereby the trunk conductors 158 and 159 are disconnected from the remainder of the trunk circuit and placed in connection with the operators calling device (Z. The irst-selector D and the Secondselector E are then operated, as explained, to establish connection with the rotary 'connectorL, which is operated by the last two digits (2 and 1) of the number 2821, to select the idletrunk line conductors 263 and exchange (Fig. 2). As'soon as the operator has finished transmitting impulses,.the key is restored to normal position, .whereby the trunk conductors 158 and '159 are extended to the cord circuit conductors 174 and 162, respectively, to terminate in the condensers 155 and 154. The operator then throws the key 7s (Fig. 1) to bridge her talking set across said conductors 174 and 162, to listen -for the called subscriber. When the side switch wiper 138 engages the grounded contact point 228 a guarding potential is established at the private wiper 126, and, therefore, at the private -contact 265, for protectswitching relay 266 -f the main manual exichange shown in Fig. 3, and at the same time an energizing circuit is closed through the relay 229 of the connector L for bridg ing the battery B3 across the trunk line leading to the-trunking operators cord circuit (Fig. 2). The circuit through the switchwing relay V266 extends from ground Grl4 to the private wiper 126, conductor 267, switching relay 266 (Fig. 3), resistance coil 268 to the battery lead 167, thence through battery B -and to ground. The circuit through the connector relay 229,' of course, goes from ground G1? to the sidejswitch wiper 138, thence through the coil 229 to the battery lead 1,67,.and to battery B (Fig. 4). The relay 266', upon energizing, operates to shift the Springs 269 and 27 O'from the springs 271 and 272 to the springs, 273 and 274. The disengagement of the said springs discon nects the drop 275 from the rotary line multiple of the trunk Conductor 264, and removes the ground'spring 271 from the vertical lin'e multiple. of the trunk conductor 263. The disengagement of the said springs connects the trunk line conductors 263 and 264 with the tip and sleeve springs of thc jack jt. When the switching relay 266 operates, as above stated, thesprings 276 and 277 also engage, whereby ground is placed `upon the jack ring 278 for giving to the operator a busy-test should she test the jack y".

while the line is busy.` When the side switch passes to third position an energizing cir-v through the sleeve conductor 263 (Fig. 2);-

armature 282, contact point 283, then through ther line drop281 to-ground. The operator at the manual exchange (Fig. 2)

throws the key k2 set across the trunk line conductors 263 and 264, and upon learning that substation A3 is deslred, inserts the plug p int the jack js. The plug p normally rests in the position shown by the dotted lines, andY when in this position the springs 293 and 294are disengaged; but when the plug is removed the said springs engage and complete a circuit through the supervisory lamp 295, said circuit extending from ground through the armature 296,- contact point 297, springs 294 and 293, lamp 295 to the battery lead 298, thence through battery B2 to ground. After the plug is inserted into the jack, as stated, the key k2 is opera-ted in the opposite direc- IUS to bridge the' operators tion, whereby a signaling current passes over the ti p-side of the line and through the substation ringer to ground. As soon as the called subscriber answers, battery current for talking purposes flows over the following circuit: from ground G15 at the rotary connector L, springs 233 and 231, coil v135, through the ringer relay springs 280a and 280 and shaft wiper`125 to the trunk conductor 264, supervisory relay 300, through the tip of the pluginI to the tip-side ofthe line, through the substation A3 to the sleeve of the plug p', to the trunk line conductor 263, connector shaft wiper 124, through the coil 134, springs 230 and 232 to the battery lead 301, thence through battery B3 and to ground. The supervisory relay 300 being included in this circuit energizes and draws its arma- .tures 296 and 282 from the contact points 297 and 283. The disengagement of the armature 282 and contact point 283 cuts off the drop 281 from the line conductor 263, and the disengagement of the armature 296 and contact point 297 breaks the circuit A through the supervisory lamp 295,4 whereby the operator is notified that the subscriber at substation A3 has answered. 1t will be seen that at the instant that the plug opis inserted in the jack jz, the substation A2 is provided with battery current for talking purposes, over the 'following circuit; from ground G17 at the trunk cord circuit through the winding 257 of the relay 261 to the springs 259 and 153, springs 173 and 172 to the sleeve of the plug p, sleeve springs of the jack y'2, through the substation transmitter and receiver, tip-spring of the jack jz, tip of the plug p, through the springs 160 and 161, springs 150 and 258, thence through the winding 260 of the relay 261 to the battery lead 146, thence through battery B and to ground. The said relay 261 energizes, thereby attracting the armature 255`\from'engagement with the contact point 254. Also, when 4the ring of the plug p engages the ring of the jack y2, a circuit is closed through the release relay 242 in series with 'the release relay 243. The circuit through the said '-relay extends from ground G16 through the jack ring of the plug, through the springs 245 and 246, through the relay 242, thence through the relay 243l to the battery lead 146, thence through battery B and t'o ground. Said relays, upon energizing,

attract their armatures 248,` 286 and 287',

and 288 and 289. The relay 242 is a quick-acting relay, and the relay 243 is a slow-,acting relay, and hence the armatures 286 and 287 disengage from theA contact A points 290 and 291 before the armatures 288.

and 289 of the relay 243 engage the ground post292. The two subscribers may hold conversation-over the heavily marked conductors, and when the subscribers restore their receivers to the switch-hooks the operators of the respective private branch exchanges sleeve side of the line, through the substaare signaled as follows: When the receiver. at substation A3, (Fig. 2) is restored the circuit which supplies. talking battery current to the said substation is broken, and

`through the lamp 295 is broken. When the receiver at substation A2 (Fig. 1) is restored, the -talking battery circuit, including the windings, 257 and 260 of the relay 261V, is broken, thus permitting the armature 255 to close in contact with the point 254, Whereby the circuit, as explained, through the supervisory lamp4 250 is closed. The glowing or display of this lamp gives to theoperator the disconnect signal. The plug p is then removed from the jack jz, whereby when` the ring of the plug disengages from the ground .ring of the jack the energizing circuit through the release relays 242 and 243 becomes broken. The said release relays denergize, but the relay 242 being a quick-acting relay, and the relay 243 a slowacting relay, as explained, the armatures 286 and 287 of the relay 242 engage the contact points 290 and 291 before the armatures 288V and 289 disengage from the ground post 292.

I rThus both trunk line conductors 158 and 159 are grounded simultaneously, which 'siniultaneo'usly energizes the vertical and rotary line relays 127 and-128 of the connector L (Fig. 4), thereby bringing about the release of the central oiice switches, as previously explained.v

1f the subscriber at substation A2 desires connection with any other substation (AJ,

i l or the branch exchange operator operates the calling device d and the central ofiice'switches in the usual manner to establish the desired connection.

At R in Fig. l there is shown a second release key which, when the button 302 is pressed, grounds both trunk line conductors 158 and 159. This arrangement is provided for anauxiliary release, should the quick and slow acting relay release fail to operate.

ln the foregoing it has. been shown how a ma-in oiiice automatic substation may be operated to establish connection with a second automatic substation at a private branch .manual exchange. Suppose, now, that it is desired to conneot'the substation A (Fig. 2) with the substation K (Fig. 3),l the number of which latter, it is assumed, is 2550. When the receiver is removed at the substation A3 a circuit is closed through the. line drop 303, extending from the battery lead 298, through the drop 303 to the tion and tip-side of the line to ground at the jack js. The operator, upon learning that an outside connection is desired, inserts the plugl p' into the jack js, which extends the substation conductors tothe trunk line a circuit -is conductors 263 and 264, whereb closed through the line drop 2%5 ('Fi 3). This circuit extends from theground at the central manualexchange through the springs 271fand 269, to the conductor 263, through the cord circuit and substation A3, back through the cord circuit to the trunk conductor' 264, springs 270 and 272, drop 275 to the battery lead 301 thence throughl battery B3 and to ground. 'l`he centraloperator, in response, inserts the plug p2 into 'the jack j", which presses the springs 303B and 304 into'contact, whereby a circuit isclosed vate through the switching relay 266'4 and a guarding potential is established at the connector private contact 265 (Fig. 4) over the conductor 267. This guarding potential protectsthe line conductors 263 and 264 from ,being seized by a subscriber calling automatically. The circuit through the switching re lay extends from ground through the springs 303a'and 304, conductor 267 to the relay 266, resistance coil 268.. and battery lead v167,

'thence'. through battery B and to ground.

This guarding potential at the connector pri- 304 to the conductor 267, thence to the private bank contact 265 -(Fig. 4),- and to all other multiple contacts. The switching relay 266,

upon energizing, operates as before, and

' when the springs 269,273 and 270, 274 engage, the trunk conductors 263 and 264 are extended to the jack j, thence through the plug p2 to the cord circuit, as' shown. The operator throws the listening key la', and

l"learning that substation K on theline #2550 isv wanted, inserts the plug p into the jack js. This operates the switching relay 305 of the line #2550 in the same manner in which the relay 266 is operated, and

places a guarding potential at the connector the switch-hook breaks the talking circuit,

whereby the supervisory relay 300 denergizes, andthe armature 282 enga es the con-- tact point 283 which'is connecte to ground through the drop 281. This ground causes an energizing current to iow from the battery B? (Fig. 3) througl the winding 308 of the relay 309 to the tip of the plug and subscriber similar to I may scrib'ers K orv I inthe ma'1n exchange, or

nk rcontacts, it willv be seen,d extends 4 from ground through the springs 303* and jack, conductorl 263, through the armature 282, contact point 283,- through the drop 281 to ground. The relay 309 now operatively energizes and draws the arniature 310 in to contact with the point 311,v whereby a circuit is closed through the supervisory lamp 312. The operator removes the plug pz'from the jack j, thus breaklng the energizing play of this lamp in turn 'ves a disconnect signal to the operator o the branch exchange. Of course, if substation I had been called instead, the operator would have established a connection with the line of substation I, and the switching relay of this line would have been pulled up instead, causing the operation o the circuits controlled thereby. Of course, just as the operator in Fig. 2 calls ,subscriber K or I, any

call the subeven the subscriber As maybe lcalled by subscriber I through the medium of the main rivate branchy exchange operator and4 the exchange operator in a well own manner. In like manner, subscriber I- may call any substation at the private branch exchange in Fig. A1 by being plugged onto a trunk to said private branch exc ange'through the cord circuit (Fig. 3) by way of norma conductors 65 and 66 (Fig. 4), which conduc` tors, of course, have multiple contacts in the connector banks'and in the manual board.

Connection between any two local sub- .vstations (Figs. 1 and 2) of the branch exchange is accom lished by means of an ordinary cord circuit.- The substation .I (Fig. I

3) may be connected with any substation in the same manner in which the trunk conductors 263 and 264 were connected, 'by

means of the cord circuit to the conductors" of substation K.

When the subscriber 'at substationl I desires'connection` with any substationA or A2 of the private `branch exchange (Fig. 1), the manual operator (Fig. 3) inserts the plug p3 into the jack corresponding to one of the trunk line multiples leading to the private branch exchan e, the multiple conductors 325, 326 and 32 (Fig. 4) for exam-` ple. When the plugps (Fig. 3) is inserted in the .jack of these conductors an energizing circuit is established through the bridgecut-olf relay 64 of the first-selector D, extending romthe allotted jack over the private conductor 327 through the relay 64 to battery B. The bridge-cut-o' relay, upon energizing, operates to disconnect the line relays 58 and 60 and to disconnect the said maecla the branch exchange. The line relay is also energized by the insertion of the plug p3 to connect the calling' line with the trunk conductors 158 and 159. that the operator at the branch exchange is not signaled until the main exchange operator rings, in this way energizing therelay 236 which in turn' operates to close a circuit through the vdrop213. The branch exchange operator, upon learning the desired connection, inserts the plug p into the jack of the desired line A or A2.

It will be observed that the line drop 119 allotted to the line of substation K has been.

cut away from the conductors 306 and 307 by the insertion of insulating strips between the springs 120 and 121, and 122 and 1,23. It w1ll also be seen by referring to Fig. 3

that the springs 122,-and 120 allotted to the cut-ofi' relay 305 are separated from the line conductors 307 and 306 by the condensers 280a and 281% This, of course, is true only after the substation 4K is operating automatically..

rFrom the foregoing it will bessen that I,

provide a working telephone system in process of reconstruction fron@ one type to another. lf the system is being changed from manual to automatic, as described and illustrated, then the private branch automatic substations are installed, as shown in Fig. 1, at the private branch exchange, and all Subscribers` lines terminating at the main exchange are provided with automatic substation equipment of the kind shown at 1 in Fig. 3, and with automatic selectors and connector contacts at the exchange or main central station. At this time'it will be seen, however, thatv the operator at the private branch exchange shown in Fig. 1, and the automatic subscribers thereof, are the only ones who can operate the said automatic connectors and selectors, as at this-time subscribers whose lines terminate directly at the main exchange can only call manually. Gradually, however, the subscribers substation equipments at the main exchange are cut-over or altered in the manner shown at K in Fig. 3, or at A in lig.` 5, and the manual equipment for these cut-'over lines is rendered inoperative for calling into the exchange, but uniformly operative for calling out therefrom. In this way the' said cut-over lines are still capable of being called manually, but can only call into the exchange automatically and are also capable of being called automatically. ln this way the automatic equipment isV prevented from It will be seenlines.

or main exchange are cut-over -in the manner shown at K in Fig. 3, so that no lines thus terminating directly at the main exchange can call manually, although they can still be called manually. When the reconstruction is completed, any subscriber at the main exchange can automatically call any other subscriber at the main exchange, and can semi-automatically call any subscriber at either of the two private., branch exchanges. A subscribers telephone line is adapted to call or be called automatically when no manual switchboard apparatus is brought into play in the establishment of connection between the calling and called A subscribers telephone line is adapted to call or be called manually when no automatic apparatus is brought into play in the establishment of connection between the calling and called lines. It will also bc seen that a vsubscribers telephone line is adapted to call or be called semi-automatically or semi-manually when both automatic into play in the establishment of connection vbetween the calling and called lines. For example, service from the main exchange to the private branch exchange shown in Fig. 2, after the reconstruction is complete, uis semiautomatic. On the other hand, service from' this partlcu-lar private branch exchange to the said mam exchange is always manual in character, and service 'from this private branch exchange to the private branch exchange shown in Fig. l is also manual. Service from the private branch exchange shown in Fig. 1 to the main. exchange is always semi-automatic, as is also true of service from this private branch exchange through the main exchange to the branch exchange shown in Fig. 2. Service between the subscribers of the branch exchange shown in Fig. 2 is purely manual, while that between the subscribers of the branch exchange shown in Fig. 1 is also purely manual. The two-way trunks between the private branch exchange of Fig. 1 and the main exchange.

are equippedatthe main exchange for selection and seizure either manually or automatically, but at the said private branch exchange a connection to or from any one of these trunks is purelynmanual. This is also true of the two-way trunks between the private branch exchange of Fig. 2 and the said main exchange or central station. It will also be seen, however, that'the two-way trunks between the private branch exchange of Fig. 1 and the said main exchange are equipped with operatorscalling mechanisms at the trunking cord.circuits thereof, and with automatic first-selectors at their terminals in the main exchange. In this way the said trunksor .trunk lines between the private branch exchange of Fig. 1 and the main exchange can be used for controllin the automatic equipment of the main exc ange, which isnot true of the trunks extending between the private branch exchange of Fig.`2 and the main exchanges Thus the trunks entering the main exchange from the private branch exchange of Fig. 1 terminate not only in first-selectors, but also in' trunk jacks of manual boards, and in multiple contacts or terminals of automatic rotary connectors, ,such as the connector shown at L in Fig. 4. At their other ends these trunks terminate in plugs for use in connection with the Vjacks of the sub- ,45'v the generator Y of the cord circuit, or by nectors. In this way character shown at scribers lines which terminate at the pri- ,vate branch exchange of Fig. 1, in the manner explained. The trunks which. enter the main exchange from the private branch ex' change of Fig. 2 terminate in trunk jacks of manual boards, and also in the multiple contacts or terminals of the said rotary coneach connector of the in Fig. 4 can have one level thereof' appropriated for the automatic selection of trunks leading to one private branch exchange, and can have another level thereof appropriated vfor the'automatic selection -of idle trunks leadin to the other private branch exchange. ments can, however, be adopted for enabling the automatic rotary connectors to automatically select idle trunks leading to the desired private branch exchange without departing from the `principles of `my invention.

It will-be seen thatvthe ground X at the substation I is used onl for and su rvisory purposes. he supervising, it will beseen, with this kind of a manual circuit is dependent upon the groundingof the line at the substation when the subscriber hangs up his telephone, .for thepurpose of energizin the relay of .the cord circuit, and

thereby c osing the local circuit of the lamp 312, in the manner explained. 'It will be seen that the bell 114 can be rung either by thegenerator 197 for the connectors', as

either generator is grounded at one side..

Also, the apparatus at the substation I the springs 115 and 116 are adapted to normally Acontact with each other, when the receiver is hung up, to close the said ringing and supervisory circuit through the bell.

When the line is cut over, however, it will be y Seen that the .contact between these two springs is eliminated, and the ground X is also taken olf and the bell bridged across the line circuit, in the manner shown at the subf station K, as previously explained.

.It will/be understood that IFig. 5 shows a cut-over line having a manual equipment of the kind shown for the substation K in Fig.

3. It will also be understood that this subscribers line at the substation K has an automatic' equipment of the kind shown in ther arrange- Fig. 5. In other words, each line is a cutover line, eachline being adapted for full automatic service, and having provisions for being called manually. l

It is evident that by my `invention I provide a cut-over system in whichv the service is not interrupted during the process of reconstruction` from one ltype to another.

This, obviously, is an advantage, as, it does,

not necessitate a temporary closing of the exchange andcessation of service while the system is bein remodeled.

Before the ines are cut-over-that is to say, ata substation like the one indicated at I-the selectorsfor such lines are rendered inoperative by temporarily 'disconnecting them from the battery, such as the battery B.. The subscribers at the substations thereof cannot disturb the automatic switches that is, cannot call automatically. The subscribers lines are said to be cut-over when they are ready for the new service. For example, the line ofthe substation I has both equipments, but has not beencut-over for automatic service-that is to say, it has not been cut-over'to permit the subscriberfto call into the exchange by means of automatic apparatus. The line of the substation Khas,

however, been completely cut-over, as the subscriber of this line is now in a osition to,

call or be called automatically, a though he can still be called manually. Iii other words, and although the subscriber at substation I can be called automatically by the subscriber at substation A, or by the operator at the private branch exchange, it will be seenthat the manual service over the line of the subscriber at substation I has not Ybeen disturbed in any way. For this reason the line of this substation I is not a cut-over line,

` whereas the line "of the substation: K is a cut-over line, because the' latter now has full automatic service, -and the service through the medium of his oldor manual equipment has been disturbed and 'materially curtailed or limited.

In `connection with the rotary connector L in Fig. 4 of the drawings, attention is called .to my prior applisaid'equipment inoperative for calling into" the exchange, over subscribers telephone disclosure of the I Lamme lines terminating 5in automatic exchange equipment, and incapable of interfering With the manual service While all subscribe ers telephone lines of the system are incondition for calling and being called manuall A. Working telephone system in process of reconstruction from one type to another, Without interfering with the service thereof, comprising subscribers telephone lines, automatic and manual. equipment for the exchange and substations of one or more of said lines, and suitable provisions for rendering the manual portion of said equipment inoperative for calling into the ex- -fqhange, over subscribers .telephone lines adapted to call or be called automatically, but uniformly operative for calling out therefrom, and incapable Of interfering with the automatic service after a vportion of the system is Working automatically.

3. A Working telephone system in process of reconstruction from one type to another,

without interfering With the service thereof, comprising subscribers telephone lines, automatic and manual equipment for the exchange and substations of one or more of said lines, and suitable provisions for rendering the automatic portion of said equipment inoperative for calling into the exchange, over subscribers telephone lines adapted to call or be called manually, but uniformly operative for calling out therefrom, and incapable of interfering With the manual service While a portion of the system is still Working manually.

Il. A working telephone system in process of gradual reconstruction or transition from one type to another, Without interfering with the service thereof, comprising subscribers telephone lines, automatic and manual equipment for the exchange and substations of one or more of said lines, means for calling automatically, and suitable provisions for then rendering the manual portion of said equipment inoperative for calling into the exchange, over subscribers telephone lines terminating in automatic exchange equipment, and incapable-of interfering with the automatic service after all subscribers telephone lines of this character are in condition for calling and being called automatically. i

In a Working telephone system in process of gradual reconstruction or transition from one ltype to another, Without interfering with the service thereof, the combination of subscribers telephone lines, automatic and manual equipment for the exchangeand substations of one or more of said lines. means for calling automatically, suitable provisions for then rendering the .automatic portion of said equipment inoperative for calling into the exchange, over subscribers tele )hone lines terminatine in auitomatic'exchange equipment, and incapable of interfering with the manual service While all subscribers telephone lines of the system are in condition for calling and being called, and local batteries for talking at all substations having automatic equipment, as and for the purpose set forth.

equipment 'inoperative for calling into' the exchange, over subscribers telephonelines adapted to call or be called automatically,

, but uniformly operative for calling out therefrom, and vincapable of interfering With the automatic service after a portion ofthe system is working automatically, and local batteries for talking at all substations having automaticv equipment, as and for the purpose set forth.

7. ln a working telephone system in process of reconstruction from one type to another, without interfering with the service thereof, the combination of subscribers telephone lines, automatic and manual equipment for the exchange and substations of one or more of said lines, suitable provisions for4 rendering the automatic portion of said equipment inoperatiye for calling into the exchange, o-ver subscribers telephone lines adapted to call or be called manually, but uniformly operative for calling out therefrom, and incapable of inter- .fering with the manual service While a portion of'the system is still Working manually, and local batteries for talking at all substations having automatic equipment, as and for the purpose set forth.

8. In a working telephone system in process of reconstruction from one type to another, Without interfering with the service thereof, the combination of subscribers telephone lines, automatic and manual equipment for the exchange and substations of `one or more of said lines, means forcalling manually, suitable provisions for then 'rendering the manual'portion of said equipment inoperative for calling into the exchange, over subscribers telephone lines terminating inautomatic exchange equipment, and incapable of interfering with the automatic service after all subscribers telephone lines of the system are in condition for calling and being called either automatically or semi-automatically, and local batteries for talking at all substations having automatic equipment, as and for the purpose set forth.

9. In a working telephone system in process of reconstruction from one type to another, without interfering with the service 

